This invention relates generally to a device and a method for producing an information recording disk, such as a video disc, phonograph disc or the like, and more particularly, the present invention relates to a device and a method for producing information recording disks by stamping a synthetic resin by a disk stamper.
There are various methods for producing an information recording disk, and according to one conventional method, as is disclosed in Japanese Patent publication No. 53-33244, a flat layer of a liquid molding resin is provided on a stamper, on which undulations carrying information have been made, then a sheet or flat plate functioning as a backing plate is pressed to the flat layer of the resin so that the resin layer assumes a given thickness, and the resin is hardened by irradiating a suitable ray.
According to another known method, as is disclosed in Japanese Patent provisional publication No. 53-116105, a liquid molding resin is dropped onto a stamper in advance, and a backing plate, which has been convexly deformed, is pressed toward the resin so as to stretch the resin to be flat, or while the resin is held by the convexly deformed backing plate, the air between the stamper and the backing plate is sucked throughout the periphery of the stamper so as to stretch the resin. After the resin has been stretched on the stamper, a light ray is irradiated to harden the resin. Then the hardened resin is detached from the stamper. According to another method, the backing plate is pressed by a roller so as to uniformly form a resin layer on a stamper.
However, these conventional methods for producing an information recording disk have sufferred from occurrence of air bubbles which are apt to be made in the finished products of the disks. It is easy for air bubbles to enter the liquid molding resin when the resin is placed on the stamper and when the resin is stretched by pressing the backing plate toward the stamper. Such air bubbles may result in dropout of information data in both stylus-contact and stylus-noncontact type information recording disks. Signal or data dropout in an information recording disk may result in deterioration of reproduced picture and/or sound quality. Especially in the case of a video disk, since the density of the data or signals is extremely high compared to ordinary phonograph disks, such air bubbles in the disk, which do not raise a serious problem in a phonograph disk, become a source of trouble. In the case of a video disk of the type arranged to be traced by a pickup stylus which is in contact with the surface of the disk, such air bubbles may damage the stylus. Namely, the presence of air bubbles mingled with the resin lowers the commercial value of an information recording disk.